What is the geometric mean of the sequence 1, 2, 4, 8, ______, 2n ?

  1. 2n / 2
  2. 2(n + 1) / 2
  3. 2(n + 1) - 1
  4. 2(n - 1)

Answer (Detailed Solution Below)

Option 1 : 2n / 2
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Detailed Solution

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Concept:

GM or Geometric Mean is the mean value or the central term in the set of numbers in geometric progression.

Geometric mean of a geometric sequence with 'n' terms is computed as nth root of the product of all the terms in sequence taken together.

Calculations:

Given sequence is 1, 2, 4, 8, ______, 2n

 

Rewrite the sequence, 20, 21, 22, ....2n

GM = \(\rm (2^0.2^1.2^2.2^3....2^n)^{\frac{1}{n+1}}\)

⇒GM = \(\rm (2^{0+1+2+3+....+n})^{\frac{1}{n+1}}\)

⇒GM = \(\rm (2^\frac{n(n+1)}{2})^\frac{1}{n+1}\)

⇒GM = \(\rm 2^\frac{n}{2}\)

Hence, the geometric mean of the sequence 1, 2, 4, 8, ______, 2n is \(\rm 2^\frac{n}{2}\)

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